A blind man will say, "I am half dead. This external world is nothing to me." He is alive, but because he cannot see the activity of the world he feels dead. If one pondered upon what one's life would be without all the organs to experience the external world, one would see that then one could realize "I am", but nothing else. No doubt if a person is inactive but looks at his hands and feet, he realizes that he is alive; but if he were not aware of this body his feeling would be different.